INVESTIGATIONS are continuing into a traffic crash which claimed the life of a young Pioneer Valley girl and left the close-knit community devastated.

A 12-year-old girl police identified as being from the area died at the scene of the fiery crash when two vehicles collided about 7.35pm Saturday.

Initial inquiries by police indicated speed and alcohol were not involved in the horror collision between a Subaru station wagon and a truck.

Sergeant Marshall Roper said a mother and her two children were travelling home on Mackay Eungella Rd when the family's car crashed head-on into the back of a truck carrying 20 tonnes of mill mud at Mirani.

The truck had nearly come to a stop at the Brand St intersection and was about to turn right when the car crashed into its rear, the Marian police officer-in-charge said.

Sgt Roper said investigations were continuing into the cause of the crash, which left both the mother, 31, and her son, 9, in Mackay Base Hospital.

The young boy has since been discharged. 

"We're still investigating exactly what has occurred," Sgt Roper said.

He said the Forensic Crash Unit was looking at whether the truck met safety standards, but a preliminary review indicated it seemed to be in order.

Sgt Roper was one of the first on scene, arriving about five minutes after it occurred, and described it was a devastating incident.

"The car was really well ablaze," he said.

"Everybody was out of it, and our main focus was the young girl.

"I think it was crucial (the first responders) got them out as quickly as they could in how quickly the fire spread in the vehicle."

Sgt Roper said the fatal crash on Saturday night was a painful one for the Mirani and Gargett communities.

"It's a close-knit community and there is devastation, people are absolutely devastated," he said.

"It is so unfortunate when these things happen. Sometimes accidents are accidents, and it is so tragic that in this case a life has been lost.

"Everybody has seatbelts on, it is just terribly unfortunate."

Sgt Roper said this would be a tragic Christmas for the family.

"I'm sure Christmases to come will be tragic," he said.